In theory, you can play your character any way you want and combine any skills you want to build your character. But in some games, splitting your focus between too many unrelated skills just leads to a subpar character (e.g. you may be level 10 but because of your mix of skills, you struggle a lot with lvl 10 enemies).
So, if I level up a little bit of everything, will I have issues dealing with enemies later in the game?
Best Answer
No, you shouldn't have issues. In fact, you'll probably find the game more playable than you would have if you did specialize in only one thing.
If you have a wide variety of skills, you have answers to anything the enemies could throw at you. No enemy is resistant to everything. You can use magic skills on the warriors and weapons on the mages, taking advantage of everything's weakness. If you only focused in 2-handed weapons, those heavily armored gap-closing enemies would really give you a tough time.
If you level up a bunch of non-combat skills, you're still not going to be in too far over your head. Just make sure you smith up some killer weapons.